This invention relates generally to cigar lighter devices for automobiles and the like, and more particularly to automatic cigar lighters which are sometimes called "fast lighters" and are especially intended to heat to useful incandescence in a relatively short interval of time.
In the past, many different automatic lighters have been proposed and produced. Most of them employed bimetallic spring fingers carried in a socket and adapted to engage the side surfaces of a heating element cup that was carried on the inner end of an ignitor plug. When the plug was pushed in, the spring fingers latched over the sides of the cup and established a circuit through the heating element. As the element reached useful incandescence, the bimetallic fingers became heated and spread apart to release the cup and the ignitor plug, enabling the same to retract and break the circuit.
Quite a number of refinements to this basic structure have been manufactured over the years. However, problems still would occur, as when one of the bimetallic fingers for any reason shifted in to the path of the ignitor plug while the latter was being depressed. This resulted in breakage and sometimes short-circuiting of the socket, which could cause either a blown fuse or else a burned-out wiring harness, depending on the degree of current overload protection built into the particular electrical system of the car. In other cases, the bimetallic fingers aged after prolonged use. When this occurred, the socket usually had to be replaced, in most cases involving difficult work underneath or to the rear of the dashboard. Where the socket was not readily accessible, such repair or replacement was costly and time consuming.
Typically in most automatic cigar lighters there is a waiting period of from ten to fifteen seconds following the actuation of the ignitor plug, until the heating element reaches useful incandescence and the plug snaps out in readiness for use. In the past, numerous efforts have been made to reduce this waiting time to just a few seconds. Generally, these innovative units have employed a bimetal disk that was disposed adjacent to the heating element, the disk constituting one live contact of an electric switch which was adapted to open when the element became hot. By positioning the disk right next to the element, shortened response times on the order of only several seconds have been achieved, particularly if the applied voltage exceeded the normal or continuous rating of the heating element that was employed.
Heretofore, cigar lighters of the type employing bimetallic disks all had a number of distinct disadvantages. Generally, if the contact area of the disk was at its center, the socket was arranged to mount the disk at its periphery. The mounting for the disk had to be such that it would not interfere with its flexing and snap-type movements. This imposed stringent requirements on the tolerances of both the disk and the part which carried it. Also, in some cases the disk constituted part of the "hot" side of the circuit, and thus had to be insulated from the remainder of the socket. Therefore, such mountings were often awkward and prone to malfunction in use.
In other constructions, as where the contact area of the disk was at its periphery, the mounting for the disk was by means of a stud passing through a hole in its center, and the end of the stud was staked or mushroomed to hold the disk in place. The problem with this arrangement was that the support area was too small, whereby the disk eventually loosened, causing poor electrical contact with the stud. Or, if the support area was made sufficiently large to effect a sturdy support, then its freedom of movement was impaired, interfering with its proper functioning. Since both the stud and the disk were current-carrying members, any loosening of the disk caused either excessive voltage drops, or else open circuits, resulting in a malfunction or failure of the device. If the bimetallic disk itself was employed as one actual surface contact which interrupted the circuit of the circuit-breaking switch, then there occurred burning and pitting at the points of surface contact, this resulting in both a poor electrical connection and in deterioration of the disk itself after a relatively short period of use.
Generally, the heating element of a cigar lighter of the type under consideration is carried in a metal cup at the inner end of the ignitor plug. With spiral-wound ribbon or coil type elements, the outermst convolution of the coil is as a rule secured by welding it to the annular wall of the cup. A slitted rivet or stud is disposed in the bottom of the cup, and the other end of coil is inserted and secured thereto. Since the cup constitutes a current-carrying member that is disposed in the "hot" side of the circuit, there has been required special heat-resistant, insulating materials in order to electrically isolate it from the remainder of the ignitor plug, as well as from the rivet which is in the "cold" side of the circuit. Various arrangements for mounting the cup and rivet were employed. It was found that different combinations of insulating bushings and/or washers generally met with success, as a rule. But with such constructions, of course, care had to be exercised in the assembly in order to insure proper seating of the washers, and to make certain that short-circuiting of the rivet to the cup would not occur.
U.S. Pat. No,. 3,870,857 issued to Laurence G. Horwitt shows a recent novel and improved arrangement for mounting a heating element cup and rivet, wherein the cup is insulated from the remainder of the ignitor plug by means of a mica washer. A series of nibs raised on the bottom wall of the cup is received in corresponding recesses in a transverse wall of the plug body, with the mica washer being sandwiched between the two walls. This permits the use of automatic assembly equipment, in that the nibs of the cup can become seated in the recesses of the transverse wall as a consequence of proper rotational orientation of the cup and plug body. Such patented construction has met with wide acceptance and considerable success due to the savings of labor that were achieved, while at the same time maintaining excellent reliability.